/*************************************************************************
 *                                                                       *
 * Open Dynamics Engine, Copyright (C) 2001-2003 Russell L. Smith.       *
 * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          *
 *                                                                       *
 * This library is free software; you can redistribute it and/or         *
 * modify it under the terms of EITHER:                                  *
 *   (1) The GNU Lesser General Public License as published by the Free  *
 *       Software Foundation; either version 2.1 of the License, or (at  *
 *       your option) any later version. The text of the GNU Lesser      *
 *       General Public License is included with this library in the     *
 *       file LICENSE.TXT.                                               *
 *   (2) The BSD-style license that is included with this library in     *
 *       the file LICENSE-BSD.TXT.                                       *
 *                                                                       *
 * This library is distributed in the hope that it will be useful,       *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *
 * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *
 *                                                                       *
 *************************************************************************/

/*
 *  Sweep and Prune adaptation/tweaks for ODE by Aras Pranckevicius.
 *  Additional work by David Walters
 *  Original code:
 *    OPCODE - Optimized Collision Detection
 *    Copyright (C) 2001 Pierre Terdiman
 *    Homepage: http://www.codercorner.com/Opcode.htm
 *
 *  This version does complete radix sort, not "classical" SAP. So, we
 *  have no temporal coherence, but are able to handle any movement
 *  velocities equally well.
 */

#include <ode/common.h>
#include <ode/collision_space.h>
#include <ode/collision.h>

#include "config.h"
#include "matrix.h"
#include "collision_kernel.h"
#include "collision_space_internal.h"

// Reference counting helper for radix sort global data.
//static void RadixSortRef();
//static void RadixSortDeref();


// --------------------------------------------------------------------------
//  Radix Sort Context
// --------------------------------------------------------------------------

struct RaixSortContext
{
public:
    RaixSortContext(): mCurrentSize(0), mCurrentUtilization(0), mRanksValid(false), mRanksBuffer(NULL), mPrimaryRanks(NULL) {}
    ~RaixSortContext() { FreeRanks(); }

    // OPCODE's Radix Sorting, returns a list of indices in sorted order
    const uint32* RadixSort( const float* input2, uint32 nb );

private:
    void FreeRanks();
    void AllocateRanks(sizeint nNewSize);

    void ReallocateRanksIfNecessary(sizeint nNewSize);

private:
    void SetCurrentSize(sizeint nValue) { mCurrentSize = nValue; }
    sizeint GetCurrentSize() const { return mCurrentSize; }

    void SetCurrentUtilization(sizeint nValue) { mCurrentUtilization = nValue; }
    sizeint GetCurrentUtilization() const { return mCurrentUtilization; }

    uint32 *GetRanks1() const { return mPrimaryRanks; }
    uint32 *GetRanks2() const { return mRanksBuffer + ((mRanksBuffer + mCurrentSize) - mPrimaryRanks); }
    void SwapRanks() { mPrimaryRanks = GetRanks2(); }

    bool AreRanksValid() const { return mRanksValid; }
    void InvalidateRanks() { mRanksValid = false; }
    void ValidateRanks() { mRanksValid = true; }

private:
    sizeint mCurrentSize;						//!< Current size of the indices list
    sizeint mCurrentUtilization;					//!< Current utilization of the indices list
    bool mRanksValid;
    uint32* mRanksBuffer;						//!< Two lists allocated sequentially in a single block
    uint32* mPrimaryRanks;
};

void RaixSortContext::AllocateRanks(sizeint nNewSize)
{
    dIASSERT(GetCurrentSize() == 0);

    mRanksBuffer = new uint32[2 * nNewSize];
    mPrimaryRanks = mRanksBuffer;

    SetCurrentSize(nNewSize);
}

void RaixSortContext::FreeRanks()
{
    SetCurrentSize(0);

    delete[] mRanksBuffer;
}

void RaixSortContext::ReallocateRanksIfNecessary(sizeint nNewSize)
{
    sizeint nCurUtilization = GetCurrentUtilization();

    if (nNewSize != nCurUtilization)
    {
        sizeint nCurSize = GetCurrentSize();

        if ( nNewSize > nCurSize )
        {
            // Free previously used ram
            FreeRanks();

            // Get some fresh one
            AllocateRanks(nNewSize);
        }

        InvalidateRanks();
        SetCurrentUtilization(nNewSize);
    }
}

// --------------------------------------------------------------------------
//  SAP space code
// --------------------------------------------------------------------------

struct dxSAPSpace : public dxSpace
{
    // Constructor / Destructor
    dxSAPSpace( dSpaceID _space, int sortaxis );
    ~dxSAPSpace();

    // dxSpace
    virtual dxGeom* getGeom(int i);
    virtual void add(dxGeom* g);
    virtual void remove(dxGeom* g);
    virtual void dirty(dxGeom* g);
    virtual void computeAABB();
    virtual void cleanGeoms();
    virtual void collide( void *data, dNearCallback *callback );
    virtual void collide2( void *data, dxGeom *geom, dNearCallback *callback );

private:

    //--------------------------------------------------------------------------
    // Local Declarations
    //--------------------------------------------------------------------------

    //! A generic couple structure
    struct Pair
    {
        uint32 id0;	//!< First index of the pair
        uint32 id1;	//!< Second index of the pair

        // Default and Value Constructor
        Pair() {}
        Pair( uint32 i0, uint32 i1 ) : id0( i0 ), id1( i1 ) {}
    };

    //--------------------------------------------------------------------------
    // Helpers
    //--------------------------------------------------------------------------

    /**
    *	Complete box pruning.
    *  Returns a list of overlapping pairs of boxes, each box of the pair
    *  belongs to the same set.
    *
    *	@param	count	[in] number of boxes.
    *	@param	geoms	[in] geoms of boxes.
    *	@param	pairs	[out] array of overlapping pairs.
    */
    void BoxPruning( int count, const dxGeom** geoms, dArray< Pair >& pairs );


    //--------------------------------------------------------------------------
    // Implementation Data
    //--------------------------------------------------------------------------

    // We have two lists (arrays of pointers) to dirty and clean
    // geoms. Each geom knows it's index into the corresponding list
    // (see macros above).
    dArray<dxGeom*> DirtyList; // dirty geoms
    dArray<dxGeom*> GeomList;	// clean geoms

    // For SAP, we ultimately separate "normal" geoms and the ones that have
    // infinite AABBs. No point doing SAP on infinite ones (and it doesn't handle
    // infinite geoms anyway).
    dArray<dxGeom*> TmpGeomList;	// temporary for normal geoms
    dArray<dxGeom*> TmpInfGeomList;	// temporary for geoms with infinite AABBs

    // Our sorting axes. (X,Z,Y is often best). Stored *2 for minor speedup
    // Axis indices into geom's aabb are: min=idx, max=idx+1
    uint32 ax0idx;
    uint32 ax1idx;
    uint32 ax2idx;

    // pruning position array scratch pad
    // NOTE: this is float not dReal because of the OPCODE radix sorter
    dArray< float > poslist;
    RaixSortContext	sortContext;
};

// Creation
dSpaceID dSweepAndPruneSpaceCreate( dxSpace* space, int axisorder ) {
    return new dxSAPSpace( space, axisorder );
}


//==============================================================================

#define GEOM_ENABLED(g) (((g)->gflags & GEOM_ENABLE_TEST_MASK) == GEOM_ENABLE_TEST_VALUE)

// HACK: We abuse 'next' and 'tome' members of dxGeom to store indices into dirty/geom lists.
#define GEOM_SET_DIRTY_IDX(g,idx) { (g)->next_ex = (dxGeom*)(sizeint)(idx); }
#define GEOM_SET_GEOM_IDX(g,idx) { (g)->tome_ex = (dxGeom**)(sizeint)(idx); }
#define GEOM_GET_DIRTY_IDX(g) ((int)(sizeint)(g)->next_ex)
#define GEOM_GET_GEOM_IDX(g) ((int)(sizeint)(g)->tome_ex)
#define GEOM_INVALID_IDX (-1)


/*
*  A bit of repetitive work - similar to collideAABBs, but doesn't check
*  if AABBs intersect (because SAP returns pairs with overlapping AABBs).
*/
static void collideGeomsNoAABBs( dxGeom *g1, dxGeom *g2, void *data, dNearCallback *callback )
{
    dIASSERT( (g1->gflags & GEOM_AABB_BAD)==0 );
    dIASSERT( (g2->gflags & GEOM_AABB_BAD)==0 );

    // no contacts if both geoms on the same body, and the body is not 0
    if (g1->body == g2->body && g1->body) return;

    // test if the category and collide bitfields match
    if ( ((g1->category_bits & g2->collide_bits) ||
        (g2->category_bits & g1->collide_bits)) == 0) {
            return;
    }

    dReal *bounds1 = g1->aabb;
    dReal *bounds2 = g2->aabb;

    // check if either object is able to prove that it doesn't intersect the
    // AABB of the other
    if (g1->AABBTest (g2,bounds2) == 0) return;
    if (g2->AABBTest (g1,bounds1) == 0) return;

    // the objects might actually intersect - call the space callback function
    callback (data,g1,g2);
}


dxSAPSpace::dxSAPSpace( dSpaceID _space, int axisorder ) : dxSpace( _space )
{
    type = dSweepAndPruneSpaceClass;

    // Init AABB to infinity
    aabb[0] = -dInfinity;
    aabb[1] = dInfinity;
    aabb[2] = -dInfinity;
    aabb[3] = dInfinity;
    aabb[4] = -dInfinity;
    aabb[5] = dInfinity;

    ax0idx = ( ( axisorder ) & 3 ) << 1;
    ax1idx = ( ( axisorder >> 2 ) & 3 ) << 1;
    ax2idx = ( ( axisorder >> 4 ) & 3 ) << 1;
}

dxSAPSpace::~dxSAPSpace()
{
    CHECK_NOT_LOCKED(this);
    if ( cleanup ) {
        // note that destroying each geom will call remove()
        for ( ; DirtyList.size(); dGeomDestroy( DirtyList[ 0 ] ) ) {}
        for ( ; GeomList.size(); dGeomDestroy( GeomList[ 0 ] ) ) {}
    }
    else {
        // just unhook them
        for ( ; DirtyList.size(); remove( DirtyList[ 0 ] ) ) {}
        for ( ; GeomList.size(); remove( GeomList[ 0 ] ) ) {}
    }
}

dxGeom* dxSAPSpace::getGeom( int i )
{
    dUASSERT( i >= 0 && i < count, "index out of range" );
    int dirtySize = DirtyList.size();
    if( i < dirtySize )
        return DirtyList[i];
    else
        return GeomList[i-dirtySize];
}

void dxSAPSpace::add( dxGeom* g )
{
    CHECK_NOT_LOCKED (this);
    dAASSERT(g);
    dUASSERT(g->tome_ex == 0 && g->next_ex == 0, "geom is already in a space");


    // add to dirty list
    GEOM_SET_DIRTY_IDX( g, DirtyList.size() );
    GEOM_SET_GEOM_IDX( g, GEOM_INVALID_IDX );
    DirtyList.push( g );

    dxSpace::add(g);
}

void dxSAPSpace::remove( dxGeom* g )
{
    CHECK_NOT_LOCKED(this);
    dAASSERT(g);
    dUASSERT(g->parent_space == this,"object is not in this space");

    // remove
    int dirtyIdx = GEOM_GET_DIRTY_IDX(g);
    int geomIdx = GEOM_GET_GEOM_IDX(g);
    // must be in one list, not in both
    dUASSERT(
        (dirtyIdx==GEOM_INVALID_IDX && geomIdx>=0 && geomIdx<GeomList.size()) ||
        (geomIdx==GEOM_INVALID_IDX && dirtyIdx>=0 && dirtyIdx<DirtyList.size()),
        "geom indices messed up" );
    if( dirtyIdx != GEOM_INVALID_IDX ) {
        // we're in dirty list, remove
        int dirtySize = DirtyList.size();
        if (dirtyIdx != dirtySize-1) {
            dxGeom* lastG = DirtyList[dirtySize-1];
            DirtyList[dirtyIdx] = lastG;
            GEOM_SET_DIRTY_IDX(lastG,dirtyIdx);
        }
        GEOM_SET_DIRTY_IDX(g,GEOM_INVALID_IDX);
        DirtyList.setSize( dirtySize-1 );
    } else {
        // we're in geom list, remove
        int geomSize = GeomList.size();
        if (geomIdx != geomSize-1) {
            dxGeom* lastG = GeomList[geomSize-1];
            GeomList[geomIdx] = lastG;
            GEOM_SET_GEOM_IDX(lastG,geomIdx);
        }
        GEOM_SET_GEOM_IDX(g,GEOM_INVALID_IDX);
        GeomList.setSize( geomSize-1 );
    }

    dxSpace::remove(g);
}

void dxSAPSpace::dirty( dxGeom* g )
{
    dAASSERT(g);
    dUASSERT(g->parent_space == this, "object is not in this space");

    // check if already dirtied
    int dirtyIdx = GEOM_GET_DIRTY_IDX(g);
    if( dirtyIdx != GEOM_INVALID_IDX )
        return;

    int geomIdx = GEOM_GET_GEOM_IDX(g);
    dUASSERT( geomIdx>=0 && geomIdx<GeomList.size(), "geom indices messed up" );

    // remove from geom list, place last in place of this
    int geomSize = GeomList.size();
    if (geomIdx != geomSize-1) {
        dxGeom* lastG = GeomList[geomSize-1];
        GeomList[geomIdx] = lastG;
        GEOM_SET_GEOM_IDX(lastG,geomIdx);
    }
    GeomList.setSize( geomSize-1 );

    // add to dirty list
    GEOM_SET_GEOM_IDX( g, GEOM_INVALID_IDX );
    GEOM_SET_DIRTY_IDX( g, DirtyList.size() );
    DirtyList.push( g );
}

void dxSAPSpace::computeAABB()
{
    // TODO?
}

void dxSAPSpace::cleanGeoms()
{
    int dirtySize = DirtyList.size();
    if( !dirtySize )
        return;

    // compute the AABBs of all dirty geoms, clear the dirty flags,
    // remove from dirty list, place into geom list
    lock_count++;

    int geomSize = GeomList.size();
    GeomList.setSize( geomSize + dirtySize ); // ensure space in geom list

    for( int i = 0; i < dirtySize; ++i ) {
        dxGeom* g = DirtyList[i];
        if( IS_SPACE(g) ) {
            ((dxSpace*)g)->cleanGeoms();
        }
        
        g->recomputeAABB();
        dIASSERT((g->gflags & GEOM_AABB_BAD) == 0);
        
        g->gflags &= ~GEOM_DIRTY;
        
        // remove from dirty list, add to geom list
        GEOM_SET_DIRTY_IDX( g, GEOM_INVALID_IDX );
        GEOM_SET_GEOM_IDX( g, geomSize + i );
        GeomList[geomSize+i] = g;
    }
    // clear dirty list
    DirtyList.setSize( 0 );

    lock_count--;
}

void dxSAPSpace::collide( void *data, dNearCallback *callback )
{
    dAASSERT (callback);

    lock_count++;

    cleanGeoms();

    // by now all geoms are in GeomList, and DirtyList must be empty
    int geom_count = GeomList.size();
    dUASSERT( geom_count == count, "geom counts messed up" );

    // separate all ENABLED geoms into infinite AABBs and normal AABBs
    TmpGeomList.setSize(0);
    TmpInfGeomList.setSize(0);
    int axis0max = ax0idx + 1;
    for( int i = 0; i < geom_count; ++i ) {
        dxGeom* g = GeomList[i];
        if( !GEOM_ENABLED(g) ) // skip disabled ones
            continue;
        const dReal& amax = g->aabb[axis0max];
        if( amax == dInfinity ) // HACK? probably not...
            TmpInfGeomList.push( g );
        else
            TmpGeomList.push( g );
    }

    // do SAP on normal AABBs
    dArray< Pair > overlapBoxes;
    int tmp_geom_count = TmpGeomList.size();
    if ( tmp_geom_count > 0 )
    {
        // Generate a list of overlapping boxes
        BoxPruning( tmp_geom_count, (const dxGeom**)TmpGeomList.data(), overlapBoxes );
    }

    // collide overlapping
    int overlapCount = overlapBoxes.size();
    for( int j = 0; j < overlapCount; ++j )
    {
        const Pair& pair = overlapBoxes[ j ];
        dxGeom* g1 = TmpGeomList[ pair.id0 ];
        dxGeom* g2 = TmpGeomList[ pair.id1 ];
        collideGeomsNoAABBs( g1, g2, data, callback );
    }

    int infSize = TmpInfGeomList.size();
    int normSize = TmpGeomList.size();
    int m, n;

    for ( m = 0; m < infSize; ++m )
    {
        dxGeom* g1 = TmpInfGeomList[ m ];

        // collide infinite ones
        for( n = m+1; n < infSize; ++n ) {
            dxGeom* g2 = TmpInfGeomList[n];
            collideGeomsNoAABBs( g1, g2, data, callback );
        }

        // collide infinite ones with normal ones
        for( n = 0; n < normSize; ++n ) {
            dxGeom* g2 = TmpGeomList[n];
            collideGeomsNoAABBs( g1, g2, data, callback );
        }
    }

    lock_count--;
}

void dxSAPSpace::collide2( void *data, dxGeom *geom, dNearCallback *callback )
{
    dAASSERT (geom && callback);

    // TODO: This is just a simple N^2 implementation

    lock_count++;

    cleanGeoms();
    geom->recomputeAABB();

    // intersect bounding boxes
    int geom_count = GeomList.size();
    for ( int i = 0; i < geom_count; ++i ) {
        dxGeom* g = GeomList[i];
        if ( GEOM_ENABLED(g) )
            collideAABBs (g,geom,data,callback);
    }

    lock_count--;
}


void dxSAPSpace::BoxPruning( int count, const dxGeom** geoms, dArray< Pair >& pairs )
{
    // Size the poslist (+1 for infinity end cap)
    poslist.setSize( count );

    // 1) Build main list using the primary axis
    //  NOTE: uses floats instead of dReals because that's what radix sort wants
    for( int i = 0; i < count; ++i )
        poslist[ i ] = (float)TmpGeomList[i]->aabb[ ax0idx ];

    // 2) Sort the list
    const uint32* Sorted = sortContext.RadixSort( poslist.data(), count );

    // 3) Prune the list
    const uint32* const LastSorted = Sorted + count;
    const uint32* RunningAddress = Sorted;

    bool bExitLoop;
    Pair IndexPair;
    while ( Sorted < LastSorted )
    {
        IndexPair.id0 = *Sorted++;

        // empty, this loop just advances RunningAddress
        for (bExitLoop = false; poslist[*RunningAddress++] < poslist[IndexPair.id0]; )
        {
            if (RunningAddress == LastSorted)
            {
                bExitLoop = true;
                break;
            }
        }

        if ( bExitLoop || RunningAddress == LastSorted) // Not a bug!!!
        {
            break;
        }

        const float idx0ax0max = (float)geoms[IndexPair.id0]->aabb[ax0idx+1]; // To avoid wrong decisions caused by rounding errors, cast the AABB element to float similarly as we did at the function beginning
        const dReal idx0ax1max = geoms[IndexPair.id0]->aabb[ax1idx+1];
        const dReal idx0ax2max = geoms[IndexPair.id0]->aabb[ax2idx+1];

        for (const uint32* RunningAddress2 = RunningAddress; poslist[ IndexPair.id1 = *RunningAddress2++ ] <= idx0ax0max; )
        {
            const dReal* aabb0 = geoms[ IndexPair.id0 ]->aabb;
            const dReal* aabb1 = geoms[ IndexPair.id1 ]->aabb;

            // Intersection?
            if ( idx0ax1max >= aabb1[ax1idx] && aabb1[ax1idx+1] >= aabb0[ax1idx] 
                && idx0ax2max >= aabb1[ax2idx] && aabb1[ax2idx+1] >= aabb0[ax2idx] )
            {
                pairs.push( IndexPair );
            }

            if (RunningAddress2 == LastSorted)
            {
                break;
            }
        }

    } // while ( RunningAddress < LastSorted && Sorted < LastSorted )
}


//==============================================================================

//------------------------------------------------------------------------------
// Radix Sort
//------------------------------------------------------------------------------



#define CHECK_PASS_VALIDITY(pass)															\
    /* Shortcut to current counters */														\
    const uint32* CurCount = &mHistogram[pass<<8];												\
    \
    /* Reset flag. The sorting pass is supposed to be performed. (default) */				\
    bool PerformPass = true;																\
    \
    /* Check pass validity */																\
    \
    /* If all values have the same byte, sorting is useless. */								\
    /* It may happen when sorting bytes or words instead of dwords. */						\
    /* This routine actually sorts words faster than dwords, and bytes */					\
    /* faster than words. Standard running time (O(4*n))is reduced to O(2*n) */				\
    /* for words and O(n) for bytes. Running time for floats depends on actual values... */	\
    \
    /* Get first byte */																	\
    uint8 UniqueVal = *(((const uint8*)input)+pass);												\
    \
    /* Check that byte's counter */															\
    if(CurCount[UniqueVal]==nb)	PerformPass=false;

// WARNING ONLY SORTS IEEE FLOATING-POINT VALUES
const uint32* RaixSortContext::RadixSort( const float* input2, uint32 nb )
{
    union _type_cast_union
    {
        _type_cast_union(const float *floats): asFloats(floats) {}
        _type_cast_union(const uint32 *uints32): asUInts32(uints32) {}

        const float *asFloats;
        const uint32 *asUInts32;
        const uint8 *asUInts8;
    };

    const uint32* input = _type_cast_union(input2).asUInts32;

    // Resize lists if needed
    ReallocateRanksIfNecessary(nb);

    // Allocate histograms & offsets on the stack
    uint32 mHistogram[256*4];
    uint32* mLink[256];

    // Create histograms (counters). Counters for all passes are created in one run.
    // Pros:	read input buffer once instead of four times
    // Cons:	mHistogram is 4Kb instead of 1Kb
    // Floating-point values are always supposed to be signed values, so there's only one code path there.
    // Please note the floating point comparison needed for temporal coherence! Although the resulting asm code
    // is dreadful, this is surprisingly not such a performance hit - well, I suppose that's a big one on first
    // generation Pentiums....We can't make comparison on integer representations because, as Chris said, it just
    // wouldn't work with mixed positive/negative values....
    {
        /* Clear counters/histograms */
        memset(mHistogram, 0, 256*4*sizeof(uint32));

        /* Prepare to count */
        const uint8* p = _type_cast_union(input).asUInts8;
        const uint8* pe = &p[nb*4];
        uint32* h0= &mHistogram[0];		/* Histogram for first pass (LSB)	*/
        uint32* h1= &mHistogram[256];	/* Histogram for second pass		*/
        uint32* h2= &mHistogram[512];	/* Histogram for third pass			*/
        uint32* h3= &mHistogram[768];	/* Histogram for last pass (MSB)	*/

        bool AlreadySorted = true;	/* Optimism... */

        if (!AreRanksValid())
        {
            /* Prepare for temporal coherence */
            const float* Running = input2;
            float PrevVal = *Running;

            while(p!=pe)
            {
                /* Read input input2 in previous sorted order */
                float Val = *Running++;
                /* Check whether already sorted or not */
                if(Val<PrevVal)	{ AlreadySorted = false; break; } /* Early out */
                /* Update for next iteration */
                PrevVal = Val;

                /* Create histograms */
                h0[*p++]++;	h1[*p++]++;	h2[*p++]++;	h3[*p++]++;
            }

            /* If all input values are already sorted, we just have to return and leave the */
            /* previous list unchanged. That way the routine may take advantage of temporal */
            /* coherence, for example when used to sort transparent faces.					*/
            if(AlreadySorted)
            {
                uint32* const Ranks1 = GetRanks1();
                for(uint32 i=0;i<nb;i++)	Ranks1[i] = i;
                return Ranks1;
            }
        }
        else
        {
            /* Prepare for temporal coherence */
            uint32* const Ranks1 = GetRanks1();

            uint32* Indices = Ranks1;
            float PrevVal = input2[*Indices];

            while(p!=pe)
            {
                /* Read input input2 in previous sorted order */
                float Val = input2[*Indices++];
                /* Check whether already sorted or not */
                if(Val<PrevVal)	{ AlreadySorted = false; break; } /* Early out */
                /* Update for next iteration */
                PrevVal = Val;

                /* Create histograms */
                h0[*p++]++;	h1[*p++]++;	h2[*p++]++;	h3[*p++]++;
            }

            /* If all input values are already sorted, we just have to return and leave the */
            /* previous list unchanged. That way the routine may take advantage of temporal */
            /* coherence, for example when used to sort transparent faces.					*/
            if(AlreadySorted)	{ return Ranks1;	}
        }

        /* Else there has been an early out and we must finish computing the histograms */
        while(p!=pe)
        {
            /* Create histograms without the previous overhead */
            h0[*p++]++;	h1[*p++]++;	h2[*p++]++;	h3[*p++]++;
        }
    }

    // Compute #negative values involved if needed
    uint32 NbNegativeValues = 0;

    // An efficient way to compute the number of negatives values we'll have to deal with is simply to sum the 128
    // last values of the last histogram. Last histogram because that's the one for the Most Significant Byte,
    // responsible for the sign. 128 last values because the 128 first ones are related to positive numbers.
    uint32* h3= &mHistogram[768];
    for(uint32 i=128;i<256;i++)	NbNegativeValues += h3[i];	// 768 for last histogram, 128 for negative part

    // Radix sort, j is the pass number (0=LSB, 3=MSB)
    for(uint32 j=0;j<4;j++)
    {
        // Should we care about negative values?
        if(j!=3)
        {
            // Here we deal with positive values only
            CHECK_PASS_VALIDITY(j);

            if(PerformPass)
            {
                uint32* const Ranks2 = GetRanks2();
                // Create offsets
                mLink[0] = Ranks2;
                for(uint32 i=1;i<256;i++)		mLink[i] = mLink[i-1] + CurCount[i-1];

                // Perform Radix Sort
                const uint8* InputBytes = _type_cast_union(input).asUInts8;
                InputBytes += j;
                if (!AreRanksValid())
                {
                    for(uint32 i=0;i<nb;i++)
                    {
                        *mLink[InputBytes[i<<2]]++ = i;
                    }

                    ValidateRanks();
                }
                else
                {
                    uint32* const Ranks1 = GetRanks1();

                    uint32* Indices				= Ranks1;
                    uint32* const IndicesEnd	= Ranks1 + nb;
                    while(Indices!=IndicesEnd)
                    {
                        uint32 id = *Indices++;
                        *mLink[InputBytes[id<<2]]++ = id;
                    }
                }

                // Swap pointers for next pass. Valid indices - the most recent ones - are in mRanks after the swap.
                SwapRanks();
            }
        }
        else
        {
            // This is a special case to correctly handle negative values
            CHECK_PASS_VALIDITY(j);

            if(PerformPass)
            {
                uint32* const Ranks2 = GetRanks2();

                // Create biased offsets, in order for negative numbers to be sorted as well
                mLink[0] = Ranks2 + NbNegativeValues;										// First positive number takes place after the negative ones
                for(uint32 i=1;i<128;i++)		mLink[i] = mLink[i-1] + CurCount[i-1];		// 1 to 128 for positive numbers

                // We must reverse the sorting order for negative numbers!
                mLink[255] = Ranks2;
                for(uint32 i=0;i<127;i++)	mLink[254-i] = mLink[255-i] + CurCount[255-i];		// Fixing the wrong order for negative values
                for(uint32 i=128;i<256;i++)	mLink[i] += CurCount[i];							// Fixing the wrong place for negative values

                // Perform Radix Sort
                if (!AreRanksValid())
                {
                    for(uint32 i=0;i<nb;i++)
                    {
                        uint32 Radix = input[i]>>24;							// Radix byte, same as above. AND is useless here (uint32).
                        // ### cmp to be killed. Not good. Later.
                        if(Radix<128)		*mLink[Radix]++ = i;		// Number is positive, same as above
                        else				*(--mLink[Radix]) = i;		// Number is negative, flip the sorting order
                    }

                    ValidateRanks();
                }
                else
                {
                    uint32* const Ranks1 = GetRanks1();

                    for(uint32 i=0;i<nb;i++)
                    {
                        uint32 Radix = input[Ranks1[i]]>>24;							// Radix byte, same as above. AND is useless here (uint32).
                        // ### cmp to be killed. Not good. Later.
                        if(Radix<128)		*mLink[Radix]++ = Ranks1[i];		// Number is positive, same as above
                        else				*(--mLink[Radix]) = Ranks1[i];		// Number is negative, flip the sorting order
                    }
                }
                // Swap pointers for next pass. Valid indices - the most recent ones - are in mRanks after the swap.
                SwapRanks();
            }
            else
            {
                // The pass is useless, yet we still have to reverse the order of current list if all values are negative.
                if(UniqueVal>=128)
                {
                    if (!AreRanksValid())
                    {
                        uint32* const Ranks2 = GetRanks2();
                        // ###Possible?
                        for(uint32 i=0;i<nb;i++)
                        {
                            Ranks2[i] = nb-i-1;
                        }

                        ValidateRanks();
                    }
                    else
                    {
                        uint32* const Ranks1 = GetRanks1();
                        uint32* const Ranks2 = GetRanks2();
                        for(uint32 i=0;i<nb;i++)	Ranks2[i] = Ranks1[nb-i-1];
                    }

                    // Swap pointers for next pass. Valid indices - the most recent ones - are in mRanks after the swap.
                    SwapRanks();
                }
            }
        }
    }

    // Return indices
    uint32* const Ranks1 = GetRanks1();
    return Ranks1;
}

